9. Castle Clinton Was An Aquarium From 1896 to 1941

In 1896, Castle Garden became the New York City Aquarium, housing 150 specimens including exotic fish and a Beluga whale, under the auspice of the New York Zoological Society. It was popular from the very first day, with over 30,000 visitors on opening day. It remained the city’s most popular attraction until 1941, when the Park Commissioner, Robert Moses, fought to tear the historic structure down in order to build a crossing from the Battery to Brooklyn. Preservationists mobilized and the structure was designated a National Monument in 1946. You can catch a glimpse of Castle Garden in its aquarium days in this video, the oldest surviving footage of NYC landmarks.
The popular Aquarium reopened in Coney Island, leaving Castle Garden to undergo a major rehabilitation in the 1970s. Today it is administered by the National Park Service, and is used as a departure point for tourists sailing to  Ellis Island and the Statue of Liberty, with a small exhibit inside.